MATERIALS | ENGINEERING THERMOPLASTICS


The following observations were made during this phase: n No anomalies were detected in the behavior of the pipe during uncoiling and cutting;


n There was residual deformation at the extremi- ties over a length of approximately 3m;


n The measured diameter was between 89 and 89.7mm (i.e. very close to the target value of 90mm);


n Average ovalisation was greater on the outer- most coil; and,


Experimental pressure resistance points to be verified for the Solef 60512 PVDF pipes and welded assemblies


pipe extruder RYB-Elydan in France. The aim was two-fold: firstly, to validate the feasibility of coiling PVDF DN90 SDR11 (thickness of 8.2mm) and SDR17 pipes (thickness 5.4mm) onto a spool; and secondly, to verify the absence of negative impacts arising from the coiling/uncoiling on the long-term mechanical performances of the pipes.


Extrusion and spooling Given the density and stiffness of the PVDF material compared to that of more conventional polymers, such as PE, a specially designed spool was pro- duced for the experimental campaign. The target configurations identified beforehand


are summarised in the table below: DN


90 90


Thickness 8.2 5.4


SDR 11 17


The extrusion line was specially prepared in


order to extrude the PVDF pipe, including disman- tling, cleaning, preparation and tuning. A certain number of preliminary tests were necessary in order to define the operating conditions. The uncoiling phase was performed following a


three-week period of storage on an open-air site. During uncoiling, the temperature measured on the pipe (using an infrared thermometer) was very close to the ambient outdoor temperature of 30-35°C. During this phase, a visual examination was carried out in order to detect potential anomalies such as abnormal deformation and cracking. After uncoiling, the pipe was cut into 1.4m long sections, the length needed to perform pressure resistance tests.


18 PIPE & PROFILE EXTRUSION | January/February 2019


n The thicknesses were between 6.4 and 7.2mm, which correspond to SDRs of 12-14, so within the interval between the two target SDRs (11 and 17). These dimension values will be rechecked during the test campaign. The test programme will consist of testing the material, pipes (straight and curved) and welded assemblies (straight and curved components). As regards the pipes and the welded assemblies themselves, pressure resistance testing at 130°C (water within the pipe and air outside) will involve several requirement levels defined on the basis of the standardised regression curves (in accordance with ISO 10931). The objec- tive of the test programme is to relate the experi- mental points obtained to the ISO 10931 reference.


Conclusions and outlook The study shows that the coiling and uncoiling of SDR11 and SDR17 DN90 PVDF pipes is achievable under normal industrial conditions. The manufac- tured pipes should be capable of being coiled and uncoiled without any negative impacts on long- term mechanical performances on the one hand, while the pipes still satisfy the initial requirements of sufficient temperature performance. If the validation is successful, then it remains to verify that the results can be extrapolated to pipes with larger diameters – and at least to DN160 pipes. Although the cost of PVDF piping is no longer negligible relative to the overall site costs – as is the case with PE pipes, for example – a thorough Opex-Capex study will be required in order to identify the inherent advantages of this material compared to the disadvantages of the traditional steel solution.


n The co-authors of this article are: Dominique Gueugnaut, Pascal Aussant & Romauld Bouaffre (RICE GRTgaz), Philippe-Jacques Leng, Philippe Martin & Elisabetta Sartirana (Solvay Specialty Polymers) and Marc Palomares (RYB-Groupe Elydan). With acknowledgements to Guy Van Meulebeke (Solvay Specialty Polymers, Belgium) for digital analysis of the coiling of pipes onto spools.


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